Point-to-point storage protocols such as the Serial Advanced Technology Attachment (SATA) protocol support one active communication between a storage device and a host bus adaptor at a time. In a multi-host bus adaptor system, a port selector may be coupled between a plurality of host bus adaptors and the storage device to provide redundant paths by allowing the plurality of host bus adaptors to access the storage device. Although, all of the host bus adaptors may access the storage device, there can only be one active communication between one of the host bus adaptors and the storage device at any one time. The storage device is unaware of the multiple host bus adaptors.
When a connection is established between a host bus adapter and the storage device in a connection oriented environment, the host bus adapter is given exclusive access to the storage device until all of the pending commands in the storage device are complete. The current connection may be closed and another connection may be established between another one of the host bus adaptors and the storage device when all pending commands for the current host bus adaptor have completed. Thus, each host bus adaptor in a multi-host system manages their connection to a storage device to ensure that the connection is not closed until all pending commands have been completed.
A host bus adaptor having a Serial Attached Small Computer System Interface (SAS) that supports multi-host access to storage devices may communicate with a SATA device using the SATA Tunneled Protocol (STP). STP is a connection orientated protocol between an STP host or host bus adaptor and a SATA device which establishes a tunnel in a SAS environment and allows SATA Frame Information Structures (FISs) to be exchanged.
Multiple STP hosts may connect to a SATA device via several SAS expanders or multi-level SAS expanders and a STP/SATA bridge using STP. A STP/SATA bridge device is a device containing an STP target port, a SATA host port, and the functions required to forward information between the STP target port and the SATA host port to enable STP host ports in a SAS domain to communicate with SATA devices in a SATA domain. The STP/SATA may be included in one of the SAS Expanders.
When the STP/SAS bridge accepts a connection for a storage device from a STP host, the STP target in the STP/SAS bridge establishes an affiliation for the storage device to that particular STP host. The STP/SATA bridge cannot accept any connections for that storage device from any other STP host until the affiliation is cleared by the STP host or the STP/SATA bridge is reset.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments of the claimed subject matter, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly, and be defined only as set forth in the accompanying claims.